1. Field of the Invention
The present invention relates to a fluid compressor having a horizontal rotation axis, used in, e.g. a refrigeration apparatus, for sucking and compressing a low-pressure refrigerant gas and discharging a high-pressure refrigerant gas.
2. Description of the Related Art
Conventionally, there is known a horizontal fluid compressor used in, e.g. a refrigeration apparatus.
In this type of compressor, a rotor having a horizontal axis is housed within a horizontally elongated sealed casing.
An oil reservoir for a lubrication oil is formed at an inner bottom portion of the sealed casing. There is provided an oil supply device for sucking the lubrication oil from the oil reservoir in accordance with the rotation of the rotor, and supplying the oil to a compression mechanism provided at the rotor.
In a normal vertical compressor, a rotor extends vertically and its lower end portion is immersed in a lubrication oil in an oil reservoir formed at an inner bottom portion of a sealed casing. Thus, an oil supply device of this compressor can easily and surely suck the lubrication oil by utilizing a centrifugal force produced by the rotation of the rotor, and can supply the oil to a compression mechanism.
However, in the horizontal fluid compressor. The axis of the motor is horizontal and parallel to the level of the lubrication oil in the oil reservoir, and a considerable distance may be provided between the rotor and the level of the lubrication oil, depending on the compression capacity of the compressor.
Thus, n particular, the horizontal fluid compressor needs to be provided with a highly reliable oil supply device for surely sucking up the lubrication oil.
An example of the horizontal fluid compressor is a so-called helical blade fluid compressor which has a relatively simple structure and a high sealing property, and realizes high efficiency compression and easy manufacture and assembly of parts.
FIG. 14 shows an example of an oil supply device of this horizontal fluid compressor.
A lower end opening portion of an oil suck-up pipe 102 is immersed in a lubrication oil in an oil reservoir 101 formed at an inner bottom portion of a sealed casing 100.
By the influence of high-pressure gas discharged into the sealed casing 100, the level of the lubrication oil in the oil reservoir 101 is pushed and the oil is sucked up through the oil suck-up pipe 102.
The sucked-up oil is led to an oil supply port 105 formed axially in a rotor piston 104 via a space defined between a bearing 103 and an end face of a shaft portion of the rotor piston 104. The oil supply port 105 communicates with the bottom of a helical groove (not shown) along which a blade is wound. The lubrication oil is supplied to a chamber defined between the blade and the bottom of the groove.
The oil is further supplied to various parts of the compression mechanism, e.g. a slide portion between the blade and the helical groove, a slide portion between the blade and a cylinder 106, and slide portions between the bearing 103, on the one hand, and the cylinder 106 and rotor piston 104, on the other hand. Thus, smooth operation of the compression mechanism is ensured.
This oil supply device, however, has the following problems.
The lubrication oil in the oil reservoir 101 is sucked up through the oil suck-up pipe 102 by the pressure difference between the gas pressure within the sealed casing 100, into which the high-pressure refrigerant gas is discharged, and the pressure in the chamber defined by the bottom of the helical groove (i.e. the outlet of the oil supply port 105) and the blade. The position of the outlet of the oil supply port 105 is determined such that the pressure in the chamber is an intermediate pressure between the discharge pressure of the refrigerant gas and the sucking pressure.
However, the lubrication oil supplied to the chamber is led to a compression chamber defined by the blade, and in this compression chamber the oil is compressed along with the refrigerant gas. Thus, because of oil compression action, a great load is likely to occur and compression efficiency decreases.
In addition, when the compressor is stopped, the lubrication oil returns to the sucking portion owing to the pressure difference between the pressure in the chamber (i.e. The outlet of the oil supply port 105) and the pressure in the oil sucking portion.
Consequently, at the re-start time, much time is needed to supply the lubrication oil to the respective slide portions, and oil supply to, e.g. an Oldham mechanism, becomes inadequate.
When the lubrication oil reaches the compression chamber from the outlet of the oil supply port 105, the oil compression action occurs once again and a great load acts. This being the case, the reliability of this oil supply device is low.